1) Field of the Invention
The present invention relates to a technology for detecting filming of toner or additive occurring on an image carrier (a photoconductor, an intermediate transfer member, or the like) of an image forming apparatus of an electrostatic photographing type.
2) Description of the Related Art
In the field of image forming apparatuses of electrostatic photographing type, fixing of toner component to image carriers, such as photoconductors or intermediate transfer members, is called “filming”. Such filming lowers the quality of the image forming apparatus with time or reduces life of the image carrier. Various methods have been proposed to solve this problem. However, to solve this problem it is necessary to accurately detect presence of filming on the image carrier, because, accurate determination leads to reduction in operation time and less damage to the image carrier.
There are mainly two methods for detecting filming on a photoconductor. A first method includes detecting change of an amount of light reflecting from the surface of the photoconductor. A second method includes monitoring how a cleaning blade comes in contact with the photoconductor. The second method includes detecting an amount of bending of the cleaning blade, detecting an amount of displacement of a supporting shaft of the cleaning blade, and the like.
Japanese Patent Application Laid-open No. H5-273893 discloses a conventional image forming apparatus. This image forming apparatus has a light emitting element that irradiates light onto a surface of an image carrier, a first light receiving element that receives light that is regularly reflected from the surface of the image carrier, a second light receiving element that receives light that is irregularly reflected from the surface of the image carrier. A comparing unit compares the amount of light detected by the first and second light receiving elements with a reference value. A control unit controls operation of a rubbing member based on the result obtained by the comparing unit.
Japanese Patent Application Laid-open No. H6-95555 discloses another conventional image forming apparatus. This image forming apparatus includes an image carrier and a cleaning blade which abuts on the image carrier to remove residual toner. Moreover, a filming removing member that removes filming on the image carrier by coming in contact with the image carrier. A rotational angle detecting member detects a rotational angle of a rotating shaft of the cleaning blade. A filming detector detects presence of filming based on the result of detection by the rotational angle detecting member.
Japanese Patent Application Laid-open No. H8-129327 discloses still another image forming apparatus. This image forming apparatus includes a strain gauge that detects an amount of strain on a cleaning blade. An amplifier amplifies a signal output from the strain gauge to a predetermined level. The strain on the cleaning blade varies depending on friction with a photosensitive drum. Presence of filming is determined based on the output of the strain gauge.
Japanese Patent Application Laid-open No. H2003-5597 discloses another conventional image forming apparatus. This image forming apparatus includes a recording member carrier that carries and conveys a recording member, an image forming unit that forms a toner image on a recording member carried by the recording member carrier, a unit that transfers the toner image on a transfer member, and a cleaning unit that cleans the recording member carrier, where a cleaning blade itself or a clamping metal plate for the cleaning blade is mounted with a magnetic member for controlling a strain amount of the cleaning blade in a fixed range and the cleaning blade is attracted and corrected by a magnetic force of a solenoid coil provided. The cleaning blade can be directly pulled by a chuck and corrects the same.
The conventional image forming apparatuses have a problem that the parameter they measure, for detecting presence of filming, change minutely with presence of filming so that, sometimes, although there is filming, it can not be detected.
Filming does not always occur evenly on a photoconductor surface. Therefore, particularly, in detecting strain on the cleaning blade, many strain gauges must be arranged in order to achieve an even sensitivity over the whole area on which the cleaning blade abuts.
In detection of an amount of reflected light, there is also a problem that fluctuation of sensitivity due to a wavelength in such an apparatus as a color image forming apparatus becomes large, which results in a configuration too complicated to observe the whole surface of a photoconductor.